In the trades, such as the electrical trade, it is well known to use portable lasers where is it desired to extend a straight line over a significant distance, for example, for levelling, surveying or the like. It is also known to incorporate a laser into a self-centering plumb assembly such as described in U.S. Pat. No. 5,537,205 which issued to Costa `et al` on Jul. 16, 1996 for a Self Leveling Laser Plumb Assembly. Applicant is also aware of other optical plumb lines such as those disclosed in the following U.S. Pat. Nos. 3,858,984; 3,911,588; 4,183,667; 4,448,528; and 5,163,229.
Like the Costa reference, the laser plumb line of the present invention is directed to replacing manual plumb lines. Manually operated plumb lines are typically a length of string having a weighted plumb bob at one end. In the present invention, a universal joint or two-degree-of-freedom gimbal mounted laser has a weight at its lowermost end so that gravity aligns the laser vertically upwards no matter the inclination on which the base is mounted.